The present invention relates to a fuel injector.
An injection valve for fuel injection systems for internal combustion engines having a nozzle body having an inner guide bore within which a valve needle can move axially is described in German Published Patent Application No. 35 34 125. On its downstream end the valve needle has a sealing section which extends conically and which works in conjunction with a valve seat surface of the nozzle body that is also conically tapered, thus forming a seat valve. Near the conical sealing section, a plurality of metering openings are provided in a lower guide section of the valve needle and distributed around the circumference; they extend at an angle relative to the longitudinal axis of the valve so that a swirling movement is imparted upon the fuel which exits the metering openings in the direction of an injection opening. Herein, the metering openings are arranged as grooves or bores on or near the outer circumference of the axially movable valve needle.
A further fuel injector having a valve needle for opening and closing the valve that can be actuated electromagnetically is described in German Published Patent Application No. 28 07 052. This injection valve also has a nozzle body as a component of a valve housing on the downstream end of which a valve seat is arranged. The axially movable valve needle is guided in an inner bore of a tube-shaped sleeve which is inserted appropriately into the valve housing. At the lower end of the sleeve an annular body whose outer diameter is smaller than the inner diameter of the valve housing is pressed onto an annular flange. The lower end face of the annular body rests against the valve housing. A swirl chamber is created between the annular body and a closing head of the valve needle. The fuel enters the swirl chamber from an outer annular area via two metering bores which are created in the wall of the annular body and which open out tangentially into the swirl area.
A fluid valve via which fuel can be injected in a combustion chamber is described in U.S. Pat. No. 4,621,771. This valve has an actuating device via which a valve needle can be moved axially, the valve needle having a spherical closing element. In addition, the valve has a valve seat element on which a valve seat, in conjunction with which the valve closing element works, is provided. The valve needle is guided in an inner longitudinal opening of a partly conical insert element which has upstream from the valve seat means for imparting swirl to the fuel. Herein, the insert element has on its downstream end a swirl area whose outer edge is conical and which has a plurality of swirl orifices which are obliquely inclined and extend to the longitudinal opening. The insert element is used exclusively to guide the valve needle, to supply the fuel, imparted with swirl, to the valve seat. The fuel cannot flow through the insert element due to the size of the guide opening. The insert element is pressed against a conical seat surface of the valve seat element by a fastening sleeve that is screwed into the valve housing. Openings in the fastening sleeve ensure that the fuel to be conveyed can only flow along the outside of the insert element.
The fuel injector according to the present invention the advantage that highly favorable flow paths for fuel to which swirl is to be imparted are created in a particularly simple manner. Because the fuel injector has the design features according to the present invention, it has the following advantages: little pressure is lost; flow starts evenly and quickly; and the preliminary jet is very short (the jet is prepared very quickly) so that very xe2x80x9ccleanxe2x80x9d jet profiles can be created. The conical outer edge of the swirl area of the swirl insert and the swirl grooves which open out to the valve seat guarantee that the flow is not sharply deflected when it exits the swirl grooves in the direction of the valve seat. The flow immediately follows the (conical) seat edge in an advantageous manner. In addition, it is advantageous that only a very small swirl chamber volume is present. In addition to the short, favorable flow path already mentioned, which permits very quick jet preparation, the fuel injector according to the present invention has the advantage that it ensures increased linearity of the injection quantity during the injection period.
Further advantages are that the swirl insert is simple and inexpensive to manufacture. In addition, injection values, e.g., the static injection quantity and the jet angle, can be modified subsequently in a very straightforward manner by enlarging the swirl grooves.
An improved seal in the area of the conical wall of the through-opening of the valve seat element and the conical outer edge of the swirl area of the swirl insert can be achieved if a sealing edge that is arranged at an angle relative to the conical edge is created on the outer edge of the swirl area.